1. Field of the Invention
This invention relates generally to improvements in document shredding machines and the cutter assemblies used therewith. More particularly, this invention relates to miniaturized energy efficient document shredding apparatus for handling light duty shredding tasks.
2. Description of the Prior Art
Generally in the art there have been developed document shredding machine arranged to receive documents fed into a cutter assembly; and therein cut, chop and shred the documents using opposing high speed cutting wheels. One of the earliest of such machines is represented by the U.S. Pat. No. 1,178,386 issued to Edwards in 1916. In his device there is described opposing cutting wheels having blades protruding on the periphery, thereof. These are arranged to intermesh while rotating at high speed and thereby cut documents dropped therebetween. Since that basic design, the opposing cutting wheels have been in general use. The U.S. Pat. No. 1,319,496 issued to Stachowski in 1919 describes an improvement on the Edwards dual rotating cutters by adding means to strip the cut material from the intermeshing cutting wheels. This prevents jamming and feeds the material into a waste chute.
Advance in this art has been quite slow and is exemplified by the 1940 improvement patent (U.S. Pat. No. 2,202,843) issued again to Edwards. He improved the mounting of the rotating cutters, improved the strippers and added a feed chute. Thereafter, and it wasn't until approximately ten years later, in 1951, that another improvement (U.S. Pat. No. 2,554,114) proposed modified stationary combers fitting within the rotating knife blades of the old dual roller blade system. This kept the blades clear of debris and further prevented malfunction.
Since those old designs were completed there was very little activity until recently. The U.S. Pat. No. 4,018,392 issued to Wagner proposed an improved mounting for the dual rotating cutters and again another improvement in the combing mechanism. In 1981, another improvement to the cutter mechanism was proposed by Hatanaka in U.S. Pat. No. 4,260,115 which provided a dramatic change in the appearance of the shredded product. This confetti cut is obtained with a combination of the dual rotating blades against horizontal stationary spacers to provide the cross cut. This design represented an improvement of a transverse cutting system patented in 1971 (U.S. Pat. No. 3,620,461) which required separate cutting operations for the longitudinal and transverse cutting.
More recent improvements have dealt with anti-clogging and anti-jamming mechanisms. In U.S. Pat. No. 4,330,092 there is provided means for adjusting the overlap between the two cutter blade assemblies to help prevent clogging. Similarily, in the U.S. Pat. No. 4,411,391 issued to Crane, an improvement is described where one of the cutting rollers is movable so that thick or uncuttable material will pass through the dual rotating cutting rollers instead of jamming the machine. A contrary position was taken by General Binding Corporation in its U.S. Pat. No. 4,489,897 where there is provided mounting yolks arranged to straddle the cutting blades and further support the cutting rollers. This prevents their separation regardless of the material passing therebetween.
No system heretofore proposed provides a compact energy efficient means for shredding paper which is adaptable to miniaturization. All systems proposed to date utilize high speed rotating roller mounted blades with means for frictionally scrubbing or combing the shredded paper therefrom. Typically, these have been driven through a gear or belt drive from an electrical motor, and in some cases employed a belt conveyor to feed the material to the rotating cutter blades. These designs have proved to be energy inefficient and prone to jamming and malfunction.
Accordingly it is a principal object of the present invention to provide a compact document shredding device which is extremely energy efficient and economical to manufacture.
It is another object of the present invention to provide a document shredding device which has few moving parts, low rotational inertia, and which is not prone to clogging or jamming.
It is yet another object of this invention to provide a document shredding device which may be miniaturized, hand held, and battery powered.
It is similarly an object of this invention, in a further embodiment, to provide a shredding mechanism having rollers which are yielding to allow objects to pass therethrough.
It is still a further object to provide a document shredding device which is operable at slow and safe speeds without the danger of exposed moving blades.
It is yet a further object of this invention to provide an apparatus which combines the cutting mechanism with the document conveyor mechanism to positively feed the paper through the cutter.
It is finally an object of this invention to provide apparatus which exhibits an easily replaceable cutting head in a safe cartridge form.